Flame-retardant additives and methods of making and using the same are well-known in the prior art. Flame-retardant additives are added to many polymers during processing so as to render the finished product made with such polymers resistant to ignition.
One class of flame retardants that is used extensively in industry comprises halogenated polymers of styrenic monomers. This class of materials is utilized to impart flame-retardant properties to a broad range of polymeric resins such as, for example, polyamides, polyesters such as PET and PBT, polyolefins and styrenic polymers such as HIPS, ABS, SAN, etc. An example of a commercially successful product of this class is a brominated polystyrene flame-retardant additive sold by the Ferro Corporation of Cleveland, Ohio, under the trademark PYRO-CHEK.RTM. 68PB.
U.S. Pat. No. 4,352,909 which is owned by Ferro Corporation discloses a method for producing a brominated polystyrene flame-retardant additive such as PYRO-CHEK 68PB. Additional examples of references that disclose methods for producing brominated styrenic polymers are Naarmann et al. U.S. Pat. No. 4,143,221, Diebel et al., U.S. Pat. No. 4,200,703 and Lindenschmidt et al., U.S. Pat. No. 4,360,455. Prior art methods of brominating styrenic polymers to a useful degree, as taught in the above mentioned patents, all teach the step of putting the styrenic polymer into solution by use of a solvent during the bromination step.
One class of styrenic polymers that is beginning to attain some commercial interest is syndiotactic styrenic polymers. Nakano U.S. Pat. No. 5,200,454 concerns a flame-retardant resin composition wherein the host or base polymeric resin comprises syndiotactic styrenic polymer. Nakano '454 also talks briefly of adding halogenated syndiotactic polystyrene to syndiotactic polystyrene polymeric resin. However Nakano '454 does not provide any insight whatsoever into how to produce the halogenated syndiotactic polystyrene.
The present invention provides a novel method of producing brominated syndiotactic styrenic polymer additives that display unique and improved properties as compared to additives made using conventional methods.